Household and industrial filtration and purification of water is an old and well-established process. In recent years however, with growing water quality problems worldwide, and an increase in the number of methods available for treating water, the demand for filters capable of removing a variety of water impurities has increased significantly. Constraints of cost and space, especially for filters designed for household drinking and cooking needs, make the incorporation of several purification methods in a single standard size cartridge a necessity for their widespread use. Examples of complementary purification methods are sediment filtration, activated carbon absorption of organic compounds, redox removal of chlorine and heavy metals, and microbial disinfection by iodinated resins.
This need for multiple chamber standard cartridges has recently been recognized, both for the improved efficiency achieved by an increase in the length to diameter ratio of the column of the purifying material and for the ability to incorporate several media in a single cartridge.
No practical device capable of meeting commercial needs is known from the prior art.
One device which attempted to meet this need has been produced by Multi-Filter GmbH, and consists of 2or 3concentric chambers separated by precision molded cylinders. The product has not been a success due to its high cost, the fixed size ratio of the chambers and the large percentage (-27 %) of the volume occupied by the chamber walls in a three chamber configuration. This compares with -10 % in a single chamber cartridge. Thus, much of the advantages accrued due to the improved flow efficiency and multiple media capability are lost due to the low volume of purification media capable of being incorporated in such a filter.
Another device, advertised by the Hydro-Flow Corporation, as "Tri-Dynaflow High Performance 3-way Filtration" for improved efficiency single medium filtration, has not been further marketed.
Thus, a practical multi-media cartridge design is not yet known as an article of commerce, although such a device is of considerable interest to the home water filtration industry.